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E. A. MELLINGER.

TELEPHONE SYSTEM AND APPARATUS.

APPUCATION FILED APR. 3.1906. 1,317,522. Patented Sept. 30, 1919.

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TELEPHONE SYSTEM AND APPARATUS.

APPLICATION man an. 3. I900.

Patented Sept. 30, 1919.

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E. A. MELLINGER.

TELEPHONE SYSTEM AND APPARATUS.

APPLICATION FILED APR. 3. 1906. v

Patented Sept. 30, 1919.

3 SHEETS-SHEET 3- wazdd UNITED STATES PATENT OFFICE.

EDWARD A. MELLINGER, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, T AUTOMATIC ELECTRIC COMPANY, A CORPORATION OF ILLINOIS.

TELEPHONE SYSTEM AN D APPARATUS.

Specification of Letters Patent.

Patented Sept. 30, 1919.

Application filed April 3, 1906. Serial No. 309,687.

To all whom it may concern:

Be it known that I, EDWARD A. MELI N- can, a citizen of the United States of America, and resident of Chicago, Cook county, Illinois, have invented a certain new and useful Improvement in Telephone Systems and Apparatus, of which the following is a specification.

My invention contemplates certain imn'ovemcnts on the subscribers individual trunk-selecting and connecting apparatus of an automatic or semi-automatic telephone exchange system.

Generally stated, the object of my invention is the provision of an improved and highly efiicient system of a paratus for en abling a calling telephone su bscriber to automatically select and obtain connection with an idle trunk-line or other trunking connection before any switching or connecting operations are performed in accordance with the number of the called subscriber; for, obvitmsly, an automatic trunk-selecting apparatus of this particular character can be employed in exchanges where either automatic or manual switchboards are used for completing the connections in accordance with the number of the called subscriber.

Special objects of my invention are the provision of an improved construction and arrangement whereby the individual switches of the subscribers lines are initially actuated to close connection with a pre-selected trunk-line, by the mere closing together of the two sides of the calling sulr scribers line, which line is, of course, normally open at the sub-station; the provision of an improved construction and arrangement whereby the connection with a pre-selected trunk-line is obtained positively by the energizing of a magnet in the calling subscribe-Rs individual-switch, the plunger which responds to the pull of the energized magnet. being held in its normal position by a spring; the provision of an improved construction and arrangement whereby the plungers of any individual-switches in use are positively locked in position to temporarily maintain the desired connections between the calling subscribers lines and the trunk-lines leading to the switching apparatus for completing connections in accordance with the called number: and the provision of certain details and features of improvement and novel combinations tending to increase the general efficiency and serviceabiiity of subscribers individual trunking switches of this particular character.

To the foregoing and other useful ends, my invention consists in matters hereinafter set forth and claimed.

In the accompanying drawings, Figure 1 is a diagrammatic illustration of my improved individual-switch A which is operated the instant that the subscriber to which said switch is allotted removes his receiver from the switch-hook, preparatory to making a call, by current from the central or common battery B, the master-switch C allotted to said individual-switch being shown directly beneath.

Fig. 2 is a similar view and shows the plunger-arm of the individual-switch A in an operated position.

Fig. 3, in a similar manner, shows a calling subscriber #50 and 3. called subscriber #20 connected through the individualswitch A, a connector D, and a called individual-switch A.

Fig. 4 is a diagrannnatic perspective view showing the connector-switch in detail.

The sub-station may be of any suitable, known or approved type. Said sub-station has the well-known impulse-wheel 2 provided with the usual vertical impulse-teeth 3 which are adapted to operate the vertical impulsespring 4 in such manner that the said spring may be pressed intermittently against the ground-post 5 for the purpose of sending ground impulses to the vertical-line-eonductor of the subscribers line. Furthermore, the said impulse-wheel has a rotary impulsetooth 6, which, after the vertical impulses are sent, acts upon the rotary impulse-spring 7 so that one ground impulse. is sent to the rotary-line-conductor of the subscribers line. The switch-11091: 8 will be recognized, also the cam-arms 9, 10 and 11 thereof. The cam-arm 11 controls the so-called lockingcam 12, so that when the switch hook rises, and before the dial is rotated, the insulating tip 13 upon the end of said locking-cam is driven to the inner edge of the angled section upon the end of the so-called groundspring 14, whereby when the dial (which is not shown) is pulled down by the calling subscriber the pin 15 upon the end of the lockingdog 1G raises the said locking-cam 12 a trifle more and causes the said insulating tip 13 to fall behind the said angled section upon the ground-spring 14 and permits the latter to make electric contact with a second ground-spring 17. The engagement of the said ground-springs l4 and 17, after the operation described, places the groundpost 5 in connection with ground, whereby when the subscriber releases the dial, after having pulled it down as described, the vertical impulse-teeth 3 will act first upon the reriiral impulsespring -l-, and after that the rotary impulse-tooth 6 acts upon the rotary impulse-spring 7, as described. The subscriber is, of course, provided with a trans mitter 18 and induction-coil 19, the primary winding 20 of which is ronneetcd' normally, when the switch-hook is raised, in series with said transmitter 18 and with the subscribers line; and the secondary windin 21 connected in a local closed circuit in series with the receiver 22. Furthermore, the sub-station is provided with a ringer 23 in series with a condenser 24, which ringer and condenser, when the switch-hook is down, are connect- \Cd in series across the subscribers line. When the switch-hook is down the cam 10 maintains the switch-springs l5 and 2G in contact, whereby the said ringer and condenser are maintained across the line; but the spring 25 being depressed, two other switch-springs 27 and 28 are kept normally separated, which, when the switch-hook rises, are closed while the first pair of springs 25 and 26 spring apart. It will be noticed that the said springs 27 and 28 control the connection between the two conductors of the subscribers line, through the aforesaid transmitter 18 and primary winding 20 of the induction-coil 19. Even after the switchhook is raised, since the finger 29 upon the cam-dog 16 controls the position of the spring 28, and since the said cam-dog rotates in unison with the dial, and as long as the said dial is out of normal position, the springs 27 and 28 and, therefore, the subscriber's" lineeonduetors are kept separated for the time. The signaling device whereby a subscriber may signal a called subscriber, after he has established connection, comprises a push-button 30 and a spring 31 which normally en' ages a contact-point 32; but when the push button30 is pressed the spring 31 leaves the Contact 32 and passes into engagement with the contact-point 33 which is atthat time connected with ground. The means whereby a subscriber may release the central oflice switching apparatus, after said ap'paratus is once disturbed, comprises three release-springs 34:, 35 and 36 so controlled by the cam-arm. 9 that when, the switch-hook descends the said springs are "pressed into contact, whereby both sides of the subscribers line are grounded simultaneously,

The ind viduahswitch A, as shown in Fig. 1, connected to the subscribers line #50, like all other individual-switches emp loyed in my improved systennis built about a suitable frame 37 which comprises two electromagnets- 38 and 39, the 'l ornzer known as the actuatin or trip-magnet and the latter as the re ease-magnet. Between the said magnets there is an upright l0 that supports the plungenarm l], upon the end of which latter the plunger -42 suitably pivoted by the pin Normally the said plunger-arm 41 is retained away from the pole-piece oi the trip-magnet 38 by the re trading-spring 44-, whereby the plunger 42 is retained in normal engagement with the )lllhg(1l-:-1l!flfli 4:). Said plunger-shaft is controlled by the common master-switch C and to one end of said shaft the masterswitclrcam 46 as well as the wiper 47, are rigidly secured. The said plungcrshaft 45 is provided with a longitudinal groove or irough into which the butt 48 oi the plunger snugly fits so that whenever the said sha it i5 is rotated all plunger; that may be in ri'igap'rnu-ni with said shaft arr caused to travel with the latter. Attached to the said plungcuarm i1 is an armature -19 which is attracted by the nin -net 38 whenever the latter is energized. raid magnet 38 is in addition provided with a second armature 5-0 that is pivoted at one end to the frame 2-37. The said armature 50 has an arm 51 that controls a couple of springs 52 and 5-3 for purposes which shall hereinafter be described. The said springs are also controlled by a member 54 upon the plunger-arm 4:1 in such a manner that when the said arm is attracted the springs 52 and 53 may be sepi ated. The magnet 39 has a similar arnnlture that controls the springs 56 and 57 with respect to the springs 58 and so that when the said armature 55 attracted the said springs 56 and 57 are separated, res ectively, from the springs 58 and 59. Tl i e plungenarm 41 may be looked either in its normal or in its 0 erative position by the said armature 55. f the magnet 39 were energized when the armature 41 is in normal position the rear end 60 of said armature is caught in the angled section 61 of said armature whereby the plunger-arm 41 is prevented irom carrying the plunger 42 into engagement with the individualswitch-bank E, if the magnet 38 is energized at such a time. A ain, if the armature 55 is attracted after t 1e plunger 42 is lodged in the bank E, the chamfered end 60 of the arm 4.1 is then engaged by the angled terminal 62 of the armature 55 whereby it is impossible after such engagement for the arm 41 to return to normal position until the magnet 39 is deenergized. The difi'erent looked positions of the said arm e1 are clearly shown in Fig.e2. In connection with the master-switch C, as more clearly shown in Fig. 3, there is an auxiliary-relay 63 which controls a couple of springs 64. and ()5 that are, when the said relay ($3 is energized, closed in contact, and a signal-lamp 66 is lighted to indicate that a subscribers line of a group is troubled with a grounded line. The bank E allotted to the individualswitch A is composed of tensets of springs similar to the springs 67, 68, 69, 70, 71 and 72, all of which are normally disengaged, but whenever the plunger-arm 41 is attracted by the magnet 38 the plunger 42 that carries a Wedge-like insulation cam 73 is thrust into one of said bank positions, and into engagement with one of said sets of springs, whereby the springs 68, 69 and 70, for example, are thrust into engagement with the, corresponding springs 67, 72 and 71. Each spring in each bank is properly insulated from all other springs, and since there are ten sets to each bank there will be ten springs like the spring 67, ten like the spring 68, and so on. However, the ten springs of each bank (similar to the spring 68) are all connected in multiple. as well as all the springs similar to the spring 69 and also all of the springs similar to the spring 'i'0but all of said multiple springs are separated from each other. It will be understood, of course, that in a way wellknown to those skilled in the art all corresponding springs, or sets of springs, in each bank are connected in multi is to all correspondin springs or sets 0 springs in all other ban (8 of the same group. Each bank forms a unit and the parts are all suitably held together by means of clamping-plates or other devices if desired. Of the springs of the bank E, the springs 72 and 71 constitute the terminals of one of the trunklines that terminate in the said bank, while the spring 68 constitutes the terminal of the so-called third release-trunk, which trunk includes the relay 7 4. For each trunkline there is provided a relay similar to said relay 7%, and in a decimal system of that order ten trunk-lines for each set of one hundred subscribers to each of such group there will be allotted, of course, ten such relays.

The master-switch C is of a well-known type. To the said switch there is allotted a bank comprising ten or a suitable number of bank-contacts a and a common metallic plate 75. The wiper 47 is designed to engage the said contacts a one at a time and to thereby connect the particular contact a, eugaged with the common plate 75. The movement of the wiper 47 is accomplished through the medium of the ratchet-wheel 76 that is provided with a number of pins 77, 78, 79 and 80 with which the cam 46 operates, engaging one of said pins one at a time in a well'known manner. Said ratchetwheel is operated by ratchet and pawl mechanism, which pawl 81 is carried by the intcrrupier-arm 82 of the motor-magnet 83. Said magnet 83 is in a normally open circuit including the interru iter-springs 84 and 85 and the rclay-springsSfi and 87. When said niagi'ict 83 is energized the armature 82 is attracted and the circuit interrupted at the springs 8st and 85; but the interruption does not occur until the end of the attractive stroke of said armature, in any suitable manner well-known to those skilled in the art. By means of said ratchet and pawl mechanism the wiper i7 is advanced one step at a time for purposes to be hereinafter described. The circuit controlling relay 88 of the master-switch C that controls the energizing circuit of the motor-magnet 83, through the medium of the springs 86 and S7, is connected in series with an auxiliaryrelay 89 which. through the medium of the springs 90 and 91, controls the energizing circuit for the trip-magnet 38. It will be clear that backward rotation of the ratchet wheel 76 is checked by the pawl 92 and that each step given to the said ratchet-wheel is made positive and definite by the guide-- post 93. As is well understood, each of the contact-points a is allotted to one of the trunk-lines leading from the individualswitch-bauks; and each time one of said trunks is occupied by some individual-switch the corresponding one of said bank-contacts a of the mastenswitch is supplied with a guarding potential to prevent the wiper 1'? from stopping upon such a contact when it is busy. The trunk-line shown terminating in the springs 72 and 71, for instance. is allotted a contact-point 9i, and the guarding potential to that contact-point is established whenever the relay '74: is energized, at which time the springs 95 and 96 are forced into contact, and the said contact-point 9+. is placed in communication with the nongrounded terminal of battery B. The method of operation of the individualswitch A and of the circuits controlled by said switch. will be described.

As already stated, the connector-switch 1), shown in Figs. 3 and 4, may be of any suitable, known or approved type, and I have elected to describe my invention in connection with the connector-switch herein shown. Said connector is of the general type described in Patent No. 815,176 granted March 13, 1906, the circuits being changed with reference to common battery work. Said connector is, therefore, of the common battery type, and is provided with the usual switch-shaft 97 by means of which the linewipers 98 and 99 and the private-wiper 100 are raised to any one of ten levels and retated onto any one of ten sets of bank-contacts. Said hue-wipers are adapted to engage the line-bank 101 and the private-wiper 100 is adapted to engage the private-bank 102. The said switch-shaft carries, as usual,

a cam 103 and a set of longitudinal teeth 101 and a set of circular teeth 165, which latter are traversed by a longitudinal slot 106 into which the end of the shaft-rest 107 normally projects. Furthermore, the said switch-shaft carries the Well-known normal-post-arm 108 that controls the switchshaft-springs 109 and 110. Said shaft is retained in normal position, with the normal-post-arm 108 against the normahpost 111, by the coil-spring 112, which latter has the inner end thereof secured to the said switch-shaft, and the other end to the normal-post 111. The operative magnets that is, the vertical-magnet 113 the rotary-magnet 114, the releasemagnet 115, as well as the private-magnet 116 and ringer-relay 117are controlled by means of the vertical and rotary line-relays 118 and 119, respectively. The said connector i provided uith a. difl'erential-relay 126 for releasing! purposes. and with a douhlo-n'ouml hackbridge-relay 121 that controls the supply of talking current to the calling subscriber.

- The vertical-line-relay when energized is adapted to press the. line-relay-spring 122 onto the ground-spring 123 and the trunkrelease-spring 124 in the direction of the second trunk-release-spring 125. The rotaryline-relay 119 in turn, when energized. pres es the line-relay-spring 126 onto the said ground'spring 123 and allows the trnnk-release-spring 125 to flex in the dime tion of the aforesaid trunk-release-spring 124. The adjustment is sueh that when both of the line-relays 11S and 119 are energized simultaneously the trunk-release-springs 12-1 and 125 come into contact for releasing the switches, as will be described. The privatemagnet 116 controls the private-springs 127, 128, 129 and 130 as usual, and the former two of said springs (127 and 128) are normally in contact While the springs 129 and 130 are normally out of contact. When the private-magnet is energized, however, the last two of said springs'elose in engagement and the first two flex apart. The ringerrelay 117 is given control over the ringerrelay-springs 131 and 132, whereby the spring 131 when the said ringer-relay is energized, 1S separated from the spring 133 and pressed onto the spring 134, and at the same time the spring 132 is pressed onto the spring 135. This operation of the ringerrelay laces the ringer-generator 136 across the ca led subseribers line, thus ringing the said called subscriber ov'er circuits to be described. As is well-known, when the vertioa'l-magnet 113 is energized the first time the so-called' release-link 137 that normally locks the double-dog 138 in normal position is withdrawn from engagement with said double-dog, so that the latter by force of the retracting-spring 139 is rotated about the pivots 140, at which time the vertical-dog 141 is placed in working en%sgement with the circular teeth 105, and he rotary-(log 142 is placed in working engagement with the longitudinal teeth 104. The double-dog 138 being thus release/tithe vertical-dog 141 supports the shaft 97 at Whatever position the vertical-n'iagnet 113, by mean's oi the verticahpawl 143, may raise the shaft 97. And likewise, afterbeing raised, the rotarydog 142 retains the sli'ait'in whatever rotary position the said shaft 97 may be rotated by the rotary-magnet114 through the medium of the rotary-pawl 144. The releasen'iagnet 115, whenever energized, attracts its armature 145, which latter "with the elongated portion 146 strikes the double-dog 138 to the right of the bearings 140 and deprives the shaft of its su )port, at the same time restoring the Weil-lniown side-switch l to normal positioi'i, moving it about the pivots 147 through the medium oi the arm 14R and the side-switeh-link 149. Said side-switch. as usual, comprises a number of siile-swii'chwipers 150, 151, 152 and 153 which a re adapted to be switched into any one of three positions. In the first position the said wipers are retained in engagement with the contact-points 154, 155,156 and 157; and in the second position in eng'ageme'nt with the contact-points 155, 156, 15 and 158; and in the third position in engageinent with the contact-points 1.59, 160, 161 and 162 The side-sWitch-arm 163 is provided atits right extremity with the so called escapementfinger 164, which latter is controlled by the eseapemen't device upon the armature 165 of the private-magnet 116. Said escapement device comprises four teeth 166, 167, 168 and 169, the first two teeth and the last two teeth being slightly out of alignment. The said escapement is designed to reduce the outward movements of the connector-sideswitch to a step-by-step operation u'nderthe retracting tension of the spring 170. When the side-switch is infirst position the escapenient-finger 164 is retained behind the tooth 168, when in second pos'ititiii behind the tooth169', and when in thethiid position in engagement With the S1d8-SW1l3Ch-Si3013"171. The diiferential-relay 120is given control of three springs 172, 173 and 174 so that'whe'n the said relay is energized th'e sringr 17.3 that normal'l engages the springl 2 is Withdrawn there rein and pressed instead in engagement with the spring 174. Siinilafrly, the double-Wound relay 121 controls three springs 175, 176 and 177. Said relay when energized forces the s'priii 176 that normally engages the s'pring 17 away from said spring and into engagement instead With the spring 177.

When the subscriber at the sub-station #50, in calling sub-station removes his receiver 22 from the switch-hook 8, as previously described, he causes the springs'27 and 28 to come into contact and the springs 25 and 26 to separate. This follows from the fact that the cam-arm 10 leaves the spring 25. The closure of said springs establisheS an energizing circuit for the tripmagne, 38. It will be assumed that the set of s irings of the bank E, shown in Fig. 1, is the first set of springs in said bank, and, of course, at such a, time, the wiper 47 of the master-switch will be in en agement with the contact-point 94, maintalningi the said contact with the common plate 75. The current that energizes the said trip-magnet 38, at the removal of the receiver, comes from ground G1 at the i'naster-switch C through the springs 91 and 90, and through the said tripmagnet 38, springs 59 and 57, rotary-line-conductor 176, primary winding 20, and transmitter 18 to the vertical-lineeonductor 177, thence through the springs 56 and 58 and through the auxiliary-role 63 to the battery-lead 178, to the non-grounc ed teri'ninal of battery B and to ground G. The said magnet 38 becoming magnetized attracts both armatures 49 and 50, the former against the tension of the retracting-spring 44 and the latter against the tension of the spring 53. The tension of the last said spring is so slight that the armature 50 responds very quickly and ahead of the armature 49. Therefore, thesprings 52 and 53 are brought into contact by the arm 51 when the armature 50 is attracted. As a result the auxiliary-relay 63 and the line-conductors 176- and 177, together with the primary Winding 20 and transmitter 18, are shunted out of the energizing circuit for the magnet 38. The energizing circuit in this last case for the said magnet 38 extends from ground G through the said magnet and through the springs 52 and 53 to the non-grounded terminal of battery B to ground G. At once the magnetizing power in the magnet 38 is increased to a great extent, and the arm ture 49 responds by driving the plunger 42 between the springs 68 and 69, so that the said springs are respectively pressed into engagement with the springs 67 and 72 and at the same time the spring is forced onto the spring 71. It will be noticed that/the great advantage presented by the use of the springs 52 and 53 is that if the line-conductors 176 and 177 are long and the resistance out on the line is great the magnet 38 will not receive enough power to attract the armature 49 against the tension of the retracting-spring 44. Therefore, I provide means whereby the action of the plunger-arm 41 becomes positive irrespective of the resistance of the outside lines and circuits. By the time that the plunger 42 is driven home in the bank E the armature 49 strikes th pole of the magnet 38, as shown in Fig. 2, and the member 54 then separates the springs 52 and 53 and restores the original circuit to the said magnet 38 through the transmitter at the sub-station. At the instant that the springs 67 and 68 are driven into contact an energizing circuit for the release-magnet 39 is set up through the springs 179 and 180 at the connector-switch D. The said springs are controlled by a release-relay 180 and the former of said springs is connected to ground and normally in contact with the spring 180. The energizing current flows from ground G at the connector D and through the springs 179 and 180, third trunk-conductor 181, relay 74, individual bank-springs 68 and 67, conductor 182 and release-magnet 39 to the battery-lead 178 and to the nongrounded terminal of battery B and to ground G. The said release-magnet 39 then attracts its armatur 55 and locks the plunger-arm 41 in a position shown by the full lines in Fig. 2, and at the same time separates the springs 56 and 57, respectively, from the springs 58 and 59. The object in separating the springs 52 and 53 after the armature 49 is attracted is to destroy-the circuit that supplies the magnet 38 with a strong magnetizing current, since after the said armature is once attracted and in contact with the pole-piece the first energizing circuit is sufficiently strong to maintain it there until the magnet 39 is energized. But even this weak energizing circuit through the said magnet 38 is destroyed when the magnet 39 separates the springs 57 and 59. It is obvious that it will be useless to maintain said energizing circuit, since the armature 62, as shown in Fig. 2, retains the arm 41 in its operative position. When the springs 58 and 56 are separated at the same time the energizing circuit through the auxiliary-relay 63 is destroyed and the off-normal lamp 66 goes out. The object in providing said lamp will be made clear. Therefore, the simple raising of the subscribers switch-hook oper ates the individual-switch A, so that the magnet 38 operates the plunger 42, which latter in turn energizes the release-magnet 39 to retain the armature 41 depressed, and to destroy the energizing circuit through itself. hlaintaining the plun or 42 in this position in the bank E, as escribed, and thereby maintaining the springs 69 and 70, respectively, in contact with the springs 72 and 71, extends the subscribers line to the conductors 183 and 184, and, therefore, to the connector D, as clearly shown in Fig. 3. The energizing circuit 4 for the releasemagnet 39 being provided through the ma net 74 as long as the said magnet 39 is energized, the magnet 74 will be energized also, and a guarding potential will, therefore, be maintained at the contact-point 94 to prevent the master-switch from placing the idle wipers opposite the seized trunkline, so that no other subscriber may be able to seize upo thesnid line. U pen the establishment (if said guarding potential the aux- ,iliin' y i'chiy '89 is energized 'simulteneoiisly With the'circuit controlling rehty 88. The Qher izing 'of the, letter closes an energizing circint' through the motor-magnet 83, so that the :trn iitnre 82 is nttrneted once end the Wiper 4-7 driven onto the eontm't-point 18."). If'the said contact is also busy the said wi )er will be driven onto the next contact forthe same reason nd so on until. the w ser-47 arriyes on a Contact that is withoui gunrding potential. The object of providin the rfi y 89 is as follows: Ass-nine thgit etore' e indiv dual switch A selzes the tri lnk-I'neithet eorre sponde to the conttiet-p oint' the immediately succeeding half o'z'en contacts, for example; are hnsy, then n hen said trunk isseized, as descllbQ lv tlre wiper e7 will driven onto the first be amen 185 and from husy contact onto husy Contact until an idle contact is fdlind. It requires some little time to accomplish this end to prevent in the meanwhile any other suhscriher from enel' g'iziiig his trip-ingnct and tllOl'Ollj. seizing one of the said hiisy trunk-lines, all of the trip-n gign ts corresponding to the trip-mugnet 38, offt "e group to'whicl the individuat switch A Belongs aretelnporarjly disconneeted from the groiind ter ninalGi which is iifiimen to r ll of the. in dividuel-switches ojth'e senie'g'ro-up. And in this m ner the busy I trflnlolines areproteeted I aga nst seizlire y aimin suhscrihers a]; the tune that the n ester-sWiteh-wiper 47 may be pass ng over the contac t pol nts corresponding to said busy, trunkdines. The energizing 01F cult for these-id, relays 88 end, 89 is from ground (1 through the said relays S8 and 89 to the common plate 75, through the wiper 4;? to the COlltACil-POllli) (when the trunk-line is first seized) through the emen. and 9 t ithe et g -1 d .178, n. tqt i fimrg wnd t ter m ba t y B am; to groundG. he ene rgiznigcircuit for the lnotoi magnet 83 181F011}, ground G through the springs 86 and through ei mean t sp 'm s and and to? t et rn H mel h r er blished, connection with he conneetonD the subscriber then begins y turnln g h s dial first fonihe numhenQ, thergby grounding the vrti-eal: twice, and then newide tvr- 7 after tl ieit roteryeli ne-eqnduetor 176 once. Groundingthe vertlcetlme-conductor tiiiice energizes the vertioal-line-relity 118 of the connector, twice and a current passes from ground G tlgrough the ground-springs 14; endli', ground-poet 5, vertiealimpulsespring 4,verticnl-line;conductor 177, inch. viduet hank-springs 9, and 72, verticaltrunk-conductor 183, vertical-line-relay 118, Winding 186 of the differential-relay 120 to the buttery-lend 178 and to the non-grounded terminal ot bettery ll and to ground G. Not only is the vertical-linereley 118 enernixed, but the (llffQl'GIltlitl-lelt 120 as Well; tint at this stage of the operation said energizatlion of the (llflll'ulliilttl]Glil- 120 is of no signiliczmce. The line-relay 118 being energized twice the line-relay-springs 122 and i543 are pressed into eontnet. twice, thereby establishing an energizing circuit ouch time through the verticalanaguet 113 from i-mind (11, through the said line-springs and through the private-springs 128 and 127, side-swilch-wiper 150, contact-point 154, ei'ticnl-niegnet 12-3 to the battery-lend 178 and to the non-grounded terminal of but- Lery B and to ground G. eing energized twice the vertical-magnet 113 attracts its armnture twice and thereby raises the shaft 97 two steps thereby placing the SWitQlLSlHlft-Wi[)GITS 98, 99 and 100 opp eite thefirst contact of the second level of their respective banks. The grounding of the I'Otfll'y-lll1BL0il(lH(t()l' 176 that follows energizes the rotary-liuerehiy 119 once through it circuit that extends from grinind G and through the ground-post 5 rotary impulse-spring 7 and 1'()i/2l1' \"lll10-C011tlllii0V 176 to the individunl-switchhank-springs and 71, thence over the rotury-truilk-conductor 184 and through the roterydinerelay 119, Winding 137 of the difl'erential-reley 120, back-b1idg6-relay-springs 176 and 175 to the battery-lead 178 and to the nongrounded terminal of battery B and to ground G. Said line-relay upon attracting its armature forces the line-relay-springs 126 and 123 into contact and thereby ener gizes the private-magnet 116 over n circuit that extends from ground G through the said line-springs and the private-1nntgnet: 116 and throu h the back-bridgerelay-springs 176 and 1 5 to the battery-lend 178 and to the non rounded terminal of battery B and to grounc G. Energizing the private-magnet once permits the side-switch retraicting spring 170 to draw the side-switch into second position and to place the side-switeh- Wiper 150 in contact with the eide-swiurh contact-point 155. Shifting said side switch, when the vertical line-conductor 177 is grounded ten times for the digit 0, causes the" vertical-'line-relay 118 to energize the rotary-magnet 114 instead of the vertical-mgnet 113enchti'me that the line-relaysprings 122 and 123 are pressed, into contact. The energizing current for said rotaryqnaqnet 114 passes from the ground terminal 1, as before, to the side-sWitch-Wiper 150, but then it extends from the contact-point 155 and through the rotary-magnet 114 to the battery-lead 178 and to the non-grounded terminal of Battery B and to ground G. The said rotarj mn qnet being energized ten times attracts its armature ten times, so that the pawl 14 i rotates the shaft 97 step-bystep ten places, thus placing the line-wipers 98 and 99 in engagement with the called subscrihcrs nornnil-conductors 188 and 189, and the privatewipcr 100 with the private-normal-conductor 190. In the same manner that the normal-conductors 1.88 and 189 connect the called subscribers line with the connector-line-bank 101 the conductors 1.91 and 192 connect the calling subscribcfs lineconductors 177 and 17 6 with the proper c0nnector-linebank. In a similar manner that the private-normal-conductor 193 connects the individual bank-spring 67 with the proper connector-private-bank-contacts, the private-normal-conductor 190 connects the corresponding bank-spring of the called individual-switch A with its connectorprivate-bank-contacts. When the rotary-line conductor 176 is grounded once for the last time the private-magnet 116 of the connector is operated once more as before. As a result the side-switch F is then drawn into third position by the retracting-spring 170 and the side-switch-wipers 150, 151, 152 and 153 pass into engagement with the contact points 159, 160, 161, and 162, respectively. The engagement of the side-switch-wipcrs 152 and 153 with the corresponding contact points 161 and 162 connects the subscribers extended conductors 183 and 184 with the called subscribers normahconductors 188 and 189, respectively, the former through the condenser 194 and the latter through the condenser 195. The engagement of the side-switch-wiper 151 with the contact-point 160 places a guarding potential at the pri vats-wiper 100 and, therefore, at the private bank-contact with which said wiper is in engagement, and at all other private-lulukcontacts connected in multiple thereto, so as to protect the called line from further seizure. The subscriber having thus extended his line into connection with the called subscribers line, he may now signal the latter subscriber by pressing the signaling-button 30, thereby grounding the vertical-line-conductor 177 when the spring 31 engages the contact-point 33. As a result the verticalline-relay 118 of the connector is energized; but since the side-switch-wiper 150 is in third position the ringer-relay 117 is ener- ,qized when the line-relay sprines 122 and 123 are premed into contact. The energizing current passes from ground G to the side-switch-wiper 150, thence through the contact-point 159, ringer-relay 117, difl'ercntialrela *-sp-rings 174 and 173 to the batterylead 178 and to the non-grounded terminal of battery B and to ground G. It is here, it will be evident. that the energization of the differential-relay 1.20 is useful for the first time by maintaining the springs 174 and 173 in contact wherebv the ringer-inlay 117 may be energized. The said clifierential-relay has been energized in series with the rotarydine-rclay 119 each time that an energizing circuit has been established through said relay, but to no purpose. The ringer-relay being energized, as stated, a current is sent over the normalconductors 188 and 189 to the called subserihefs station. and the hell of said subscriber is rung. The said current passes from the ringeugenerator 136 through the ringer-relav-springs 135 and 132, sidc-switch-wipcr 152, contactpoint 161, vertical-line-wi 'ier 98, verticaln-omial-conductor 188, vertical-line-condi1ctor 195*, condenser 196, ringer 197, springs 198 and 199, rotary-line-conductor 200, rotary-nonnal-conductcr 189, rotary-wiper 99, contact-point 162, side-switrh-wipcr 153 and ringer-relay-springs 131 and 131 to the generator 136. The called subscriber upon rcmoving his receiver 201 permits the springs 202 and 203 to come into Contact and an energizing circuit is established through the baek-bridgc-relay 121. The current in said circuit flows from ground G to the sideswitch-wiper 151. thence through the winding- 201 of the relay 121 to the ringer-relaysprings 133 and 131, side-switch-wiper 153, rotary-line-wiper 99, rotary-normalmondnctor 189, rotary-line-conductor 200, primary winding 205 of the induction-coil 206, transmitter 207, and through the springs 202 and 203 to the vertical-lineconductor 195. thence over the vertical-normalconductor 188, vertical-line-wiper 98, side-switch-Wiper 152, winding 208 of the relay 121 and through the differential-relay-springs 172 and 173 to the battery-lead 178 and to the non-ground terminal of battery B and to ground G. Of course, it will be clear that this circuit is only established when the called subscriber I'GITIOVGS the receiver from the switch-hook and after the ringern'ehiy 117 is denergizedthat is, after the calling subscriber releases his signaling-button 30. The relay 121 being energized the springs 176 and 177 are forced into contact, and as a result the transmitter 18 of the calling sub-station is provided with current. The current for energizing; said transmitter also flows from the ground G and then passes through the springs 177 and 176- and through the winding 187 of the differentialrelay 120 to the rotary-line-relay 119, thence to the ITOtElIjV-tl'llnkfiOndflttOI 184 and to the rotary-line-condnctor 176. primary winding 20 of the induction-coil 19. transmitter 18, springs 28 and 27 to the rotary-line-co-nductor 177 and thence to the vertical-trunk-conductor 183, vertical-line-relay 118, Winding 186 of the difi'erential-relay 120 to the battery-lead 178 and to the non-grounded terminal of battery B and to ground G. The windings 186 and 187 of the said difi'erel'itishrelay are so made that the current in passing in the direction thus described does not energize said relay. Therefore, the springs 173 and 172 remain in contact. The energizing circuit for the release-magnet 115 is controlled conjointly by the trunk-release-springs 124 and 125 located between the vertical and rotary line-relays 11.8 and 119, and by the difl'erential-relaysprings 178 and 17 1, so that although the said linerclays are energized during talking, and although, therefore, the trunk-releasesp'rings 124 and 125 are in contact, the encrgizing rircuit for the releasemagnet 115 is still open at the difi'erentiaLrelay-springs 17 1 and 173. The transmitters of the two subscribers being thus provided with talking battery current, in the manner Wellknown to all skilled in the art, the subscribers may now communicate with each other. Should the called subscri'hefs line for any reason be busy at the time that the calling subsr-riher attempts to close connection with the called line by grounding the rotary-lins-conductor 17 6 and thereby euen gizing the private-magnet 116. the connec tor-switch will be released. The said release occurs because the private-Wiper 100 is at such a time connected with a grounded terminal of battery B; so that when the private-magnet is energized and the springs 129 and 130 are brought into contact the releasemagnet 115 is energized. The energizing circuit extends from the battery B to a ground similar to ground G and through springs of the individual-switch A similar to the spring 67 and 68 of the individualswitch A, and to the tenth contact of the second level of the private-bank 102that is, if the subscriber #20 has made a call; or through a side-switch wiper similar to the side-switrh-Wiper 151 of the connector D (if the subscriber #20 has been called), and through the bank-1nultipling-conduetors to the tenth contact of the second level of the private-hank 102; then the current passes on to the private-wiper 100-, side-switchwiper 151, contact-point 156 (since at the time that flhe rotary-line-conductor176 is grounded for the last time the side-switch is in second position), through the privatesprings 129 and 130 to the release-magnet 115, and through the difi'erontial-relays rings 174 and 173 to the battery-lead 1 8 and to the non-grounded terminal of battery B and to ground G. The releasemagnet 115 being energized the connectorside-switch F and switch-shaft 97' are restored in a Well known manner, leaving the said side-switeh in first position and the switch-shaft in normal position. But as soon as the calling subscriber presses his signalin -butt0n he grounds the vertieal-line-con uetor 177 as stated, and thus energizes the vertical-linerelay 118 and causes the switch-shaft 97 to be raised enestepi Theswibehshaft-spmng orraine 110 and 109 now close into contact again and a busy signaling current is sent to the calling subscribefs line, notifying the said sl|b seriber that the line he desires is busy. Said busy current may be generated in the coil 20!) in any suitable manner known to the art one nd of which coil is connected to the hattery-lead 173. The busy signaling current passes from tlu: said coil 209 through the said springs 110 and 101) to the side-switch-wiper 153, thence through the condenser 195 and rotary-trimk-co-nductor 184 to the rotaryline-conductor 176, through the primary winding 20 of the induction-coil 19, vertioal-line-conductor 177, vertical.trunk-conduotor 183, vertical-line-relay 1 18, winding 186 of the differential-relay 120 to the battery-lead 17 8 and back to the coil 209. The calling subscriber then restores his rm-eiver to thesWitch-hook and grounds both the ver- 1 ieal and rotary line-conductors 177 and 176 by causing the release-springs 34, 35 and 3 6 to be pressed into contact. The said line-- ro-nductors being thus grounded the verti cal and. rotary line-relays 11R and 119 of the connector-switch D are energized simultaneously; and not only are the said rel ays energized, but the differential-relay 120 as Well. The current through each of the windings 0f the said differential-relay passes in such a direction that the said coils reinforce or augment each other. The current through the winding 186 of said diflerential-relay passes fromground Gr to the rclease-spring 34 and through the release-spring 35 to the vertical-line-conductor 177, thence through the connectorvertical line relay 118 and. Winding 186 of the difl erentialu'el'ay 120- to the batterydead 178 and to the non-grounded terminal of battery B and to ground G. Through the Winding 187 the current passes from ground G to the release spring 34, thence through the springs 3-5 and 36 to the rotary-line-conductor 176 and through the rotary-line-relay 119, winding 187 and back bridge-relay-springs 176 and 17 5 to the battery-lea-d 178 and to the nomgrounded-terininal of battery B and to ground G. When the said line-relays 118 and 1 19' are energized the sprin 124 and "125are pressed into contact, an since the difl'erentiaI-YeIaysprings 174 and 173 are in engagement at the same time the Iel-easemiagnet 115 is energized in series with the releasefrelaiy 180. The said relay 180 upon attracting its armature separates the springs 179 and 180, and as a result the energizing circuit through the trunk-releaserconduetor 1181, relay 74;, individual bank-springs'68 and 67 andthrou h the release-magnet 39 of the individual!- switch A, is then destroyed. The result is that the guarding potential at the masterswitch contact-point 94.- is removed at the instant that the, springs 95 and 96 regain their normal positions, whereby the control over the trunk-conductors 183 and 184 is abandoned and at the smile time the release-magnet 39 being deenergized permits the releasearmature 55, under the tension of the springs 56 and 57, to disengage from the terminal 60 of the plunger-arm 41, and a result the retracting-spring 44 restores the plunger 42 to normal position and permits the subscribers line-conductors 177 and 176 to be disconnected from the trunkline-conductors 183 and 184; and also, by the removing of said plunger, the trunk-release-springs 67 and 68 are forced apart in order that the energizing circuit through the release-magnet 39 may not be reestablished when the connector-release-relay 180 is de'energized. The energization of the release-magnet 115, as described, produces a restoration of the con nector-sWitch-shaft and side-switch, and as soon as the individual bank-springs 69 and 72 and 70 and 71 separate, then all the energized magnets of the connector are restored also, wherefore all the switches are fully restored to normal condition. It has been described that when the subscriber #50 established connection with the line of the sub scriber #20 a guarding potential was established at the private-Wiper 100 and, therefore, at the private-normal-conductor 190. This guarding potential not only protects the called line from further seizure, as described, but causes an energizing circuit to be established through the bridge-cut-ofl or release-magnet 210 of the individual-switch A so as to cause said release-magnet to attract its armature 211 for the purpose of separating the springs 212 and 213 from the springs 214 and 215, respectively. In this manner the said release-ma et 210 is made to act as a bridge-cut-oif-re ay, whereby the energizing circuit for the trip-magnet 216 is destroyed in order that when the called sub scriber removes his receiver from the switchhook the individual-switch A of the called line may not be operated to interfere with the connection established. Also, by separating the springs 212 and 214, the auxiliary-relay 217 is prevented from energizing uselessly and from causing the lamp 218 to be lighted unnecessarily. After the subscribers are through communicating, if the calling subscriber restores his receiver to his switch-hook he will restore the switches as before, but the circuits employed in the release are slightly different from the circuits pointed out in the preceding. For instance, when the calling subscriber restores his receiver to the switch-hook the cam-arm 10 engages the spring 25 and thereby causes the springs 27 and 28 to separate before the cam arm 9 forces the release-spring 34 onto the release-sprin 35. As soon as the said springs 27 an 28 spring apart the energizing circuit through the transmitter 18 and, therefore,- through the vertical and. rotary line-relays 118 and 119 is destroyed. The said relays then regain their normal positions, but immediately after the ground-releusc-sprin 34 is forced onto the Verticalrr-lease-spring 35, thereby grounding the vertical-line-conductor 177, causing the vertiral-line-relay 118 and the diffcrcntiahrelay 120 to be energized. The latter relay upon energizing forces the springs 173 and 174 into contact and thereby closes one of the normally open switch-points in the energizing circuit of the releasemagnet 115. As soon as the differential-relay springs 172 and 173 are separated the back-bridge-relay 121 is dee'nergized, which latter then permits the springs 175 and 176 to come into contact Meanwhile the switch-hook has descended far enough to press all the release-springs into contact and to ground the rotary-lineconduetor 176 also. As a result the rotaryline-relay 119 is energized and a current is sent through the Winding 187 of the difl'erential-relay 120, Which strengthens the already energized differential-relay. The vertical and rotary line-relays 118 and 119 being energized at the same time the trunk-release-springs 124 and 125 are closed in contact, whereby the last normally open switchpoint in the energizing circuit of the releasemagnet 115 is closed. The said release-ma net receives current then from ground 5 through the trunk-release-springs 124 and 125, release-relay 180*, through the said release-magnet and differential-relay-springs 174 and 173 to the battery-lead 178, to the non-grounded terminal of battery B and to ground G. It will be evident that both the release-magnet 115 and release-relay 180 are energized simultaneously. The effect of energizing the latter relay has already been describedthat is, the individual-switch A is restored to normal position and a guarding potential at the master-switch bank-contact 94 is removed. At the same time the connector-switch-shaft and side-switch and relays and magnets re restored to normal condition. The object of providing the auxiliary-relay 63 and the lamp 66 at the individual-switch is to indicate at the central office Whenever the vertical-line-conductor 177 becomes grounded in case of accident. The relay 63 would be energized by current flowing from ground to said vertical-line-conductor 177, thence through the springs 56 and 58 and the said coil 63 to the battery-lead 178 and to the non-grounded terminal of battery B and to ground G. Said relay will then attract its armature and cause the lamp 66 to flash and stay lighted as long as the said ground remains n the line. One of said relays is usually provided for a group of individual-switches numbering ten, twenty, fifty, or even one-hundred or more if desired. Since it is absolutely essential that the longitudinal slot upon. the plungerheift 46, near which all of the individualswitches are arranged, should not rotate beyond a, point that will make it in'ipossible for the butt end 48 of the plunger 42 to return to its soeket at any time, the oscillations of said shnl't are, therefore, S0 controlled by the pins 77, 78, 79 and 80 upon the ratchetwheel "(6 of thenuuster-switch C that it a plnhger leagves the plunger-shaft at one extreme position and then tries to return when the said shaft. is at the o Posite extreme positionit will find no di cultv in adjusting itselli inppoper contact therewith. Care is taken that the sand pins on the ratchet-wl'ieel 76- shall oscill e the cam 46 just so far and no farther. I aving fullydescribed my improved individual-switch it will be evident that it is adapted to be used not only for conrnion battery work but forlocal battery work as Well. One of the features is the provision of the quick-noting armature 50 for the trip-magnet 38, and of the more slowly acting armature 49 that is attached to the plunger-and 41. The armature 5U first perates and then provides a, stronger energizing. circuit for operating the armature 49-, w iich latter armature being attracted connects the-calling subscribers line with any desired trunk-line, depending upon the position to which the plunger-shaft 45 has rotated. or positioned all idle plunger-s. An ene ggiwing'circui-t is then as a result, estab'- lished forthe release-magnet 39, which latin turn operates to destroy the energizmg circuit throught he original magnet 38.

Tlieinagnets employed in my improved individual-sWitch may be wound to any suit able strength. For instance, the triponagr net 38 may be wound to 100 ohms; the bridgecut-oli' and release-magnet 39 to 1000 ohms; the release-trunk-relay 74 to 60 ohms the ground signul relay 63 to one ohm;. end in themaste1-sw1toh the motor-ma net 83to 6,.Qohn1s, the circuit controlling re 88 to 1.000 ohms, and the auxiliary-relay 89 to It .will he understood, of course, that the exclninge can; beyenlerged by interposing. onev or more selectors between the indiyidualsw tches the connectors, in the wellknowii mannerl F {inconvenience of illustration however Iliave jelected to show the individual swite ,trun lines'- running direct to connectors, thus illustratin a comparativel y ezi changze' in wh ch each sub seriberls number consists. only of two digits. Should the egtcliange'ibe enlarged to a ccoinmodiate more s scr bes necessitating the use of three digit num rs, then selectors would beused. between the indiyidualswitches; the 'oonnectors. A still furie e e te nt .e w ite nstth -n s f. four digit numbers, would reguirefirstend' second selectors; Alll'this, however, will be rend'ily understood and necd not be further 65 described.

W itlnry improved ztl'l'ttllgfll'lll-Ellt the subscribers" individual-switches are operated autome-tically when the subscribers start to call, the more closure of the metallic line circuit at any railing subscriber's station being sitflicicnt to initiate the operation of the calling subscribers ii'ldividunl-switch, thus automatically placing his line in connection with the pro-selected idle trunkline. In this way, the preliminary trunking; has all been HlCL'OlllPllSllGCl by the time the calling subscriber begins calling the number of the called subscribefls substation. During conversation the calling subscribers indiridual-switoh remains energized by the temporarily closed local circuit through the nmgnet 39, which letter must be de'cnergized when it is desired to restore the individualswitch und thus vacate the trunk-line tom porztrily appropriated for use between the individunl-switch and the connector or other switch. With the arrangement shown, it will be seen that this local circuit for main-- tnining the energized condition of the magnot 89 during conversation is controlled by the. relay 180*, which latter is energized when the line-relays 118 and 119 and the difi'ercntial-relny 120 are energized by the act of the calling subscriber in hanging up his receiver. As illustrated, thereis a relay 180 for each connector, The relays 74 are, however, each individual to one of the trunln ln'irs running fronrtlie group of individualswitches to the connectors or other switches,

and consequently these relays T l are enoh individual to one of the contacts in the mustcr'switch. Each relay 72L when onorgized places aguarding potential at its allotted bank-contact in the master-switch or ew-itelroperating meehine employed for selectively: operating the difl'erent individual-switches of the group to which it he longs. In this way, the guarding potential forthe mastenswitch comes fron tlie nonr grounded pole oftho buttery, While in the cornieetor shown the guarding potential for producing the automatic busy release in case the. called line is busy comesdronr the grini'nded pole of the battery. The battery B is norinnlly bridged across theterminals of each sub-scribefls'line For example, the calling subscribers line has one side normally oonnected with the grounded vpole of the battery tl'iroughthe mecliuni 'of the magwhicli latter is common to all oftlie ines 125,

in the group. In this way the line 'energiz ingrircmt for initially actuating the individual-switch includes the calling sub-- scribers transmitter 18, the primary of the induction-coil, the contacts of the push-button 30, and the contacts of the hook-switch, as previously described. The battery bridge thus normally existing across the end or terminal of eac subscribers line is controlled by the magnet 39 allotted to such line. Of course, it will be understood that these bridges are not individual to the lines, inasmuch each bridge includes the battery B, which latter of course, is common to all of the lines in the exchange, or at least common to all oil the lines in the group. During conversation, however, the battery is inbridge of the talking circuit through the medium of relays allotted to the connector. My improved trunking apparatus and machinery for enabling a calling subscriber to automatically obtain connection with a pro-selected trunk-line, or with any other idle trunking or trunklikc connectioin. before calling the desired number or before giving the order for the desired number, can be used in either automatic or semi-automatic exchanges and in connection with either automatic or manual switchboard apparatus for completing the connections in accordance with the called number. In any event, however, and particularly if the system is of the common battery type, the said batter is normally in bridge of each subscriber's line, and this bridging is through the medium of the said trunking machinery or apparatus. In other words, the battery is preferably normally connected with both sides of the subscribers line through the medium of certain coils or windings of the automatic trunk-selecting and connecting apparatus in which the subscribers lines terminate. In my improved arrangement there are only two electro-magnets which are individualthat is to say, each sub-scribers line has allotted to it only two electro-magnets, thus materially simplifying the trunking apparatus. Economy and eiliciency are obtained by adapting each magnet to act not only as a relay but also as an actuatingnmgnet, whereby each magnet not only controls certain circuits, but also has a certain degree of control over the plunger.

With my improved arrangement an accidental or abnormal grounding of a subscribers line will not operate the individualswitch of such line. In other words, each individual-switch is operated by a line-circuit including both sides of the line in seriesthat is to say, a metallic circuit is used for initiating the operation of the individualswitch. Consequently, as stated, the accidental or abnormal grounding of one or mprasubscribe lines will not throw the indiudualevito i inta-or atieni n w not mr r u ll .11; min

v tie up: an)" 1 r nk ine ii Such accidental or abnormal grounding of the lines will be instantly indicated by the supervisory lamp-signal 66, it being understood that one of these lamps can be allotted to each group of subscribers. It will also be seen that each group of subscribers can be divided into sub-groups, and another lamp allotted to each sub-group, thus rendering it comparatively easy to find the lines which are grounded. The selectors and connectors or any other switching machinery which may be provided are subsequently operated by grounded line-circuitsthat is to Say, after the operation of the individuahswitch by the calling subscriber, through the medium of the metallic circuit, all subsequent switchin operations are accomplished by grounde line-circuits which include the ground between the exchange and the substation of the calling line. Thus, grounded circuits can be used for operating all of the switching machinery except the switching device for making the first selection of an idle trunkdine, and for this first switch a metallic energizing circuit can be provided, thus precluding the liability of one or more of the trunk-lines leading from the individual-switches being temporarily tied up by the accidental or abnormal grounding of one or more of the subscribers lines. In other words, if grounded circuits are used for initiating the operation of the individual-switches, it naturally follows that an accidental or abnormal grounding of any line will operate the individual-switch thereof, causing the latter to make connection with the selected trunk-line, thus keeping this selected trunk-line out of use until the trouble can be remedied. With my improved arrangement, however, as explained, the trunk-lines leading from the indlviduah switches are not subject to this kind of trouble.

What I claim as my invention is:

l. A telephone system comprising a calling subscribers line-conductors normally open at the subscribers station, idle trunklines, and an automatic selectively operated individual-switch allotted to the subscribers line, adapted for connecting the line with any one of said idle trunk-lines, means for maintaining said switch normally ready and selectively positioned to perform the said connection whenever the subscriber closes his line-conductors together and thereb sends electric current through the indivi ual-switch.

2. A telephone system comprising a calling subscrrbers hue-conductors normally open at the subscribers station, idle trunklines, and an automatic selectively operated individual-switch provided with a terminal bank to which the said trunk-lines are connected, said individual-switchadapted to be .1 Mi ,r

M LU

operated b the said subscriber for connect his' l'i'n withuiiy one of said idle trunklines, means rep mtintsinirrg said switch normall ra'dy and selectively positioned to make the sai'd"contie'ctioh Wher'iever the subscriber closes his li'neconductors to getlicr and thereby sends electric current througli' the indlridiial switch.

3. A t'ele nhone system comprising a calling subscribers hue-conductors normally Open at the subscribers station, and terminat'i'ng' sit the other-end in an individual sv'vitch, a luralit of trunk-lines, a switch ing devlceiczipttble of establishing connection between the said subscribers line and any one of said truhk-lihes, coiii'prisin means for searching" for an idle trunkinc and means for maintaining said switch normally ready and selectively positioned to ma'ke the said coiihectioh whenever the subscriber closes his line-conductors together and therebj" sends electric current through the individual-switch.

4. A tele piione system comprising a call ing subscribers talking circuit conductors normally open at the subscribers station, trunk-lines, af subscribers individual-switch provided with a plunger and plilner-controinng isiigii'e seminar for estc trunk and a; coi resIi'onHihgl lirie'teriniiiall for each trunk in saidfswitch, and an energizing ohshit for said magnet, comprising the tail:- irig ciriiift conductors, wh reby the sand magnetpitty be energized to positively operate and chose Said pluiiger to connect the said line with any one o said trunk-lines.

5. A telephone system Comprising ca'lling subscribers telking circuit conductors normally open at the subscribers station, idle trunk-lines, and an individual-switch provided with a terminal bank, e plunger adapted to be thrust into said bank plunger-controlling magnet for oprelii said plunger, an'd'j an en rgiinifikcircuu for said Ilia" et, coinbrising the ta i'ngjcircuit conductors, each of trunlc lines' termilisting iii 'suitgble cements in siild' bank, and

the s ubseribers line terniihnting in contacts, comihrrw the s'eid' trunk-lines "but out of en ageiiient' therewith, whereby the said line It's by the op'erstiiih o the longer be connec'ed w'ith o ie ofsa'i trii 'liries.

6. RteleqibnsjSte-In comprising a calli'n'gf sheets-15ers line-conductors normally open at the. subs'bribers station, idle" trunklines, an individual-switch proi ided with a plunger, a plunger-controlling magnet, and e, pliirslity of ei'ie g'iziif" circuits for ssidi mag et, oneinelir g be two linecoriductors in sei ielsfn'r'her'eiy andfoiie 0i said' t'ruhk-lines may be connectedbysaid lengeri I "v 7. A tele fiho esyst'ein cornprismg'a call ing subscribers line-conductors normally open at the subscribers station, a plurality the said liiie of t -ui'ik-lines, a switching device provided with it Ifllifigcl" capable of being operatiit'l to cstab ish connection between the said slilr-lcribcl"s line and anyone of said trunklincs, said plunger being controlled by u pluhg'encontrolling trip-magnet, and a plurality of energizing; circuits for Said mil-g not. one coinpr'ising' the said line-conductors, and the otherzt loc'ul circuit controlled by said magnet itself.

8. A telephone system comprising a cell ing su'bScribeWs l'inec0ridii'etors normaill'v open at the subscribersstiit'ion, trunlblines, n subscribers individual-switch provided with a plunger and phiiiger controlling magnet, a terniinitl' for" each trunk and a correslibiuli r'igj line tcri'uinal for each trunk, un energizing circuit for said magnet, comprising the line-conductors in series, the said magnet adopted to be energized to operate and cause said plunger to connect the said line with any one of said trunklines, said individuitbswitch allotted to said subscribefis line, said plunger normally ready and in position to perform the said connection whene er the subscriber closes his line-conductor and thereby sends the electric current for energizing said niai'gnet.

9. A telepl'io'ne system' comprising a 6511'- ing subseribers liiie-conductors nQrnuiIlj open at the subscribers station, idle trunklines, and :in individual-switch provided with it terminal biu'il t, apliinger adapted to be thrust into sziid' bank, a pliin'gerfcontrolling uuignet foroperating said plunger, aiieii'ergiiing circuit for said magnet, co1nprising" the him-conductors in series; each of said trunk-lines terininati'ngf in suitable contacts in said bank, and the subscribers line terminating-, in contacts common to the said trunk1ines but vout of engegement therewith, whereby the said line may be cohnected with one of said truiili li'nes, said plunger norin'ally ready ahdiin position to perform the aforesaid connection Whenever the subscriber closes his line-conductors and thereb sends electric current for energiiing the said magnet.

10. In an zt'utoinatic telephonesystem, a, snbsoribers line and a trunk-line, an individual-switch provided with a plunge?- for coii'li'ectihg the, st'id subscribers line with the said truh'lz' 'line, a release-magnet end a pilingt coiitmin 'g mai'gnet provided with a-' couple of circuits, one circuit including the subscribers line-conductors in series, and the (some? circuit being local and con trolled h the said plunger-controlling mag net itsel ii 11. In ariaiitoinjtic telephone systein; a

caning; subscribers lirieQaLn'd a lur'ality of triinkines, a trunli-release-con' uctor allot: ted to e'sicli' trunk-line, an indiriduabs'witdh rotided with at bank in which the said subscribers line and trunk-lines and trunkrelease-conductors terminate, said individ- Hal-switch also provided with a plunger, :1. plungencontrolling magnet, and a release magnet, said plunger adapted when the said plunger-controlling magnet is energized to connect the said subscribcrs line with one of said trunk-lines, a couple of energizing circuits for the said plunge1'controlling magnet, one circuit controlled directly by the subscriber and comprising the subscribers linc-conductors in series, and the other circuit being local and controlled by the said releasemagnet, whereby when the subsr-riber goes to make a call the said plungercontrolling magnet is energized to connect the said subsoribers line with the said trunk-line, an energizing circuit for the said release-magnet, comprising the said trunkrelease-conductor, together with a masterswitch for selectively controlling the plunger of the said individuahswitch to main tain the same when out of use in such position that the subscribers line will be connected with an idle trunk-line when he calls, and whereby the energizing circuit of the plunger-controlling magnet is so controlled that the said plunger can never connect the subscribers line with a busy trunk-line.

12. In a telephone system, the combination of subscribers telephone lines, subscribers selectively operated individual trunking switches, trunk-lines leading from the said individual-switches, a common battery normally in bridge of each telephone line through the medium of said individualswitches, means in said switches for disconnecting both poles of the battery from the subscribers lines, and a common mechanism for controlling the selective operations of said individual switches.

13. In a telephone system, a group of subscribers telephone lines, automatic switches located at the exchange and controlled by the subscribers, adapted to enable a calling subscriber to establish connection with the called subscribers line, and a source of switch-operatin electric current normally in brid e of sec subscribers telephone line, adapte for use by any calling subscriber in automatically switching his line into connection with the called subscribers line, and a common mechanism for controlling the trunking operations of said automatic switches.

14. In a telephone system, a line, a selectively operated individual trunking switch for said line provided with an operatin magnet having a quick acting armature am a slow acting armature, a circuit-closing plunger operated by one armature, and a circuit controlled by the other armature, trunking circuits associated with said plunger, any one of which may be closed by said plunger as a result of the first closure of the line circuit.

15. In a tele hone system, a line, a selectively operate individual trunking switch for said line provided with an operating magnet having a quick acting armature and a slow acting armature, a circuit-closing plunger operated by one armature, and the circuit of same magnet controlled by both arlnatures, trunking circuits associated with said plunger, any one of which ma be closed by said lunger as a result ot the first closure of t e line circuit.

16. In a telephone system, the combination of a subscribers line, an operating mag net provided with a pair of armatures, a bridge normally across the line, a combined release and bud e-cutoff magnet, circuitclosing means to be released by said bridgecut-oif magnet, and a couple of energizing circuits for the said operatin magnet, one energizing circuit including t e subscribers line, subject to control by the said bridgecut-ofi' magnet, and the other energizing circuit controlled by the said pair of armatures, substantially as set forth.

17. In a telephone system, a group of subscribers telephone lines, automatic switching machinery controllable by the subscribers, grounded circuits for operating said switching machinery, a relay adapted to be energized by the groundin of any line, and a lamp-signal provided with a normally open circuit controlled by said relay, whereby accidental or abnormal grounding of any line is indicated by said lamp-signal.

18. In a telephone system, the combination of a group of subscribers lines, trunklines, automatic trunlcselecting and connecting switches controllable by the subscribers, a relay common to said subscribers lines, adapted to be energized by a circuit including any one of said lines, a lamp-signal provided with a normally open circuit controlled by said relay, and means for disconneptin said relay from any line in use.

a. signal associated with said switching ap paratus, common to all of said lines, adapted, to automatically indicate the presence of,

an accidental or abnormal ground on any line, a rela for controlling said slgnal, and

means for isconnecting said relay from any line in use.

20. In a telephone system, the combina tion of subscribers telephone lines, individual trunking switches for said lines,

tomatically indicate the presence of an accidental or abnormal ground on an means for disconnecting said relay from any line in use.

21. In a telephone system, individualn a telephone system, a group of sub-j scribers telephone lines, automatic switch ing apparatus controlled by the subscribers,

switc e e ma t rrsni lz ha ing ,lmn -s tucts, t plurel ity oi tron k 7 ne on tor ach ank-contnct, each trunk-line provided with a thirdcomluctor or release-trunk, relays for said releuse-tru lkS, each rela having its winding ii iclutlerl in its allotte releasetrnnlr a battery having one ole rounded, uml circuits by which any re ey W 1en energized connects its corrcs'poncllng bank-contact with the non-grounded pole of said hette'r'y, establishing nomgr oimded guarding po tentiel at such contact.

22.11111 telephone system, the combinet io n of s snbsprihers' line, an individualswitCh provided with an ari neture, releasin'g n' egins ia ridge, :1 conihrned release gintl bridgc cntrolf-nlegnet, an ogera t ng magnet for said illlllfitugt}, said by; ge ut- H" negnet p ov cleil with lneans @for loclqn said e'rins tu' re' n its nor position septed :ils'o f r l o clfnng sai ar neture n its at trigctet I p tlfiltlpll.

iliJn i1 telephone system, the CQlllllJlIltltion of a subscrihprs line, en indiv dual trunkingswitch tl'lerefor, e hriglge normnlly across saltl i 'ne, i'e easing resigns, sa ld switch prgi-idecl w th e combine. briclge-cpt-olf l rs e s seamen Illness-newsmrib 195ml; ,tsremln l n b h ai sw etness n ib enib r ce sh ee linst-s i hmssst l e dapt d! e 4.21m 1}} QR WWQRQ 1 D whee ve i e l ill @L- tl %l1l -P% n m kinge cal 24; n i; te ephgiiesystem, subscr bers lines, a plurali y of, runks, means for selecting idle trnnks hez cl of the cells euto nat e means fin connecting calling subscribers lines gvith the preselected trunks, and energiiz ing circuits by tyhlch the callnw subscribers initiate the operation of sgnfautw ins "c means, each energizing circuit 1ncluclin otlisi des' of a subscri ers line.

.l tslfieh ee yst m a p es ec idletrnnk line, anta on stic means for thus seect l g hetn z -l'me seedy? th p t ep neens co ris sneperg z ng cirein' including ,of e snbscribers llI l e for e esenn ie i t an hin Im Jn ,te snhe ie s tem t. s l t e iqle'trunlg, eutornat o me ns for t usselectssih'e tninlilme elm Qf Fa n means corn rising; {tn energ q ngc rcu t 1nclp ding bo h sides of a l ne for obtaining connection with said trunk line.

2 ,11 tql i lwee s s m, .p i 'e of trunks, ut/pine 1C I Il1nS tor selecting the first idle trunk negct in order atter the one last in use, whereb eech call ng subseriber selects? trunk fhr thenext call ng subscriber, sncl m eans com nsmgen enerm l ire tin l s we th sidesw prib fsi es is s r bh em cQ n t o'n wththfififilected idle trunk.

28. n a telephone system, the combinenew @9 .Q e yelling subwi li-ye-seeduete normally open at the suhscrlhefls ewfi on, idle trunk-lines, an uutoinntic selectively o erated imlividiml-switch zillotted to the su' scrihcrs line, adapted for connecting the line with any one of suicl idle trunk-lines, means whereby suirl switch is selectively positioned and nm'melly readyto PUlliOllIl the seid connection whenever the subscriber closes his linc-comluctors together and thereby sends electric current through the individualswitch, and means having vertical motion to select groups or divisions of the excha ge end rotnr motion to connect with a me in the seh zcted group or extending connection from the slectetl trunk-line in the direction of the cal cpl subscriber.

In a telephone system, the (:OllllllllalZlOIl of a calling snbscrihcfls linccol nluctors normolly open at the subscrihefs station, idle trunk-lines, en mltoinutic selecti\-'ely oper- '(ll'CL'l in rlivithmlswitch provided with a tel" min-n1 bank to which the said tl'lll lh-llllQS are connected, said incliriduel-switch ncleptcd to be operntetl by the suirl subscriber f r connecting his line with gn1.y o11e of said idle trink-lines, means wherehy sei cl switch selectively positioned t ndnornielly; 1; ady to t eir, the saltl connection yheneyer t s subscrl er closes his h m-conductors together nd} h r bys nd le r Wi es th ipssh.

the indiyidual-svyitch, and means l avn g vertical motion to select groups or divisioiis e expheeg .e dmts y .mQ-tisin t e neot with gt line in the selected, gron for ezrtieng ing connection from the seected tlllllliine in the direction of the called subscriber.

30. In a telephone systel n, the combination of a calling subscrihcrs Line-conductors normally open at the snhscri ers station a plurality of trunlg lines, s switchini device capable of establ shing connection etyveen h sa bs i seed M57 98? ts id trunk-lines cgrn risingineens for segrychin r id flu n imesnewlm'e yssl means is selectively positioned and normally ready rte nuk the sa wene tien w se m r the sulpscrfiher closes hisv linmcongluctQrs together and thereby sends electricrtcnrrent through the 1ind i'y'idngtlrswitch, end greens having vertical. motion to select groups, or divisions of the exchnr e snd rotary notion to connect with a ine in the selected s s p for e tend ng smi tie f m th selected trunk-line 1n the direction of the.-

celled spla s 1i er- 31. In a te ephone system, the combination f a se in u se ibe s. talk sp rs tm tlnetprs normally open at the nhscribeljs station, trunk-l nes, 2t suhscri ers i idi video-S itch, rQYide with a p unger and stin e -ce lin tmeen ts l circuit for seicl rn a gnet, a term nal for esp trunk and a corresponding line terminal for each trunk in said switch comprising the talking circuit conductors, whereby the said magnet may be ener ized to positively operate and cause said p linger to connect the said line with any one oi. said trunklines, and means having vertical motion to select groups or divisions of the exchange and rotary motion to connect with a line in the selected group for extending connection from the selected trunk-line in the direction of the called subscriber.

32. In a telephone system, the co1ubination of a calling subscrihers talking circuit conductors normally open at the subscribers station, idle trunkdines, an individualswitch provided With a terminal bank, a plunger adapted to be thrust into said bank, a plunger-controlling magnet for operating said plunger, an ener izin circuit for said magnet, comprising t c tal ting circuit conductors, each of said trunk-lines terminating in suitable contacts in said bank, and the subscribe1"s line terminating in contacts common to the said trunk-lines but out of engagement therewith, whereby the said line may by the operation of the plunger be connected with one of said trunk-lines, and means havin vertical motion to select groups or divisions of the exchange and rotary motion to connect With a line in the selected group for extending connection from the selected trunk-line in the direction of the called subscriber.

33. In a telephone system, the combination of a calling subscribers line-conductors normally open at the subscribers station, idle trunk-lines, an individual-switch provided with a plunger, a plungcr-controlling magnet, a plurality of energizing circuits for said magnet, one including the two lineconductors in series, whereby the said line and one of said trunk'lines may be connected by said plunger, and means having vertical motion to select groups or divisions of the exchange and rotary motion to connect with a line in the selected grou for extending connection from the se eeted trunk-line in the direction of the called subscriber.

34. In a telephone system, the combination of a calling subscribers line-conductors normally open at the subscribers station, a plurality of trunlclines, a switching device provided with a lunger capable of being operated to establish connectlon between the said subscribers line and any one of said trunk-lines, said plunger being controlled by a plunger-controlling trip-magnet, a plurality of energizing circults for said magnet, one comprising the said line-conductors, and the other a local circuit controlled by said magnet itself, and means having verticalmotion to select groups or divisions of the exchange and rotary motion to connect with a line in the selected group for extending connection from the selected trunk-line in the direction of the called subscriber.

35. In a telephone system, the combination of a calling suhsvribers line conductors normally open at the substation thereof, trunk lines, means having vertical motion to. select groups or divisions of the exchange and rotary motion to connect with a line in the selected group for extending connection from the selected trunk-line in the direction of the called subscriber, a subscribers individual-switch for the calling line provided with a plunger and plunger-controlling magnet, a terminal for each trunk and a corresponding line terminal for each trunk in said switch, an energizing circuit for said magnet, comprising the lineconductors in series, the said magnet adapted to be energized to operate and cause said plunger to connect the said line with any one of said trunk-lines, said plunger normally ready and in position to perform the said COHHGP- tion whenever the subscriber closes his lineconductor and thereby sends the electric current for energizing said magnet.

36. In a telephone system, the combination of a calling subscribers line-conductors normally open at the subscribers station, idle trunk-lines, means having vertical motion to select groups or divisions of the exchange and rotary motion to connect with a line in the selected group for extending connection from the selected trunk-line in the direction of the called subscriber, an individual-svvitch for the calling line provided with a terminal bank, a plunger adapted to be thrust into said bank, a plunger-controlling magnet for operatin said plunger, an energizing circuit for sai( magnet, comprising the line-conductors in series, each of said trunk-lines terminating in suitable contacts in said bank, and thesubscribers line terminating in contacts common to the said trunk-lines but out of engagement there with, whereby the said line may be connected with one of said trunk-lines, said plunger normally ready and in position to perform the aforesaid connection Whenever the subscriber closes his line conductors and thereby sends electric current for energizing the said magnet.

37. In an automatic telephone system, the combination of a subscribers line and a trunk-line, an individual-switch provided with a plunger for connecting the said subscribers line With the said trunk-line, means having vertical motion to select groups or divisions of the exchange and rotary motion to connect with a line in the selected group for extending connection from the selected trunk-line in the direction of the called subscriber, a release-magnet, and a plunger thereof for each digit of the called number, operative to transmit impulses by each oporation.

44. In a telephone system, trunklines, means for automatically selectin idle trunks ahead of the calls, a subscri ers hookswitch, and means operated over a complete metallic talking circuit to seize the reselected idle trunk-line in response to c osure of the talkino' circuit by the hook-switch.

45. A telephone system comprising a call in'g subscribers talking conductors normally open at the subscribers station, idle trunk lines, and an automatic selectively operated individual switch allotted to the subscribers line, adapted for connectinothe line with any one of said idle trunk llnes, a, ter minal for each trunk and a corres ending line terminal for each trunk in said switch, means for maintaining said switch normally ready and in position to perform the said connection through the medium of said trunks whenever the subscriber closes his talking conductors together and thereby sends electric current through the individual switch.

i6. A telephone system comprising a calling subscribers talking conductors normally open at the subscribers station, idle trunk lines, and an automatic selectively operated individual switch provided with a terminal bank to which the said trunk lines are connected, said individual switch adapted to be operated by the said subscriber for connect ing his line with any one of said. idle trunk lines, a terminal for each trunk and a corresponding line terminal for each trunk in said switch, means for maintaining said switch normally ready and in position to make the said connection through the medium of said trunks whenever the subscriber closes his talking conductors together and thereby sends electric current through the individual switch.

47, A telephone system comprising a calling subscriber's talking conductors normally open at the subscribers station, and terminating at the other end in a individual switch, a plurality of trunk lines, a switching device capable of establishing connec tion between the said subscribers line and any one of said trunk lines, a terminal for each trunk and a corresponding line termi nal for each trunk in said switch, said switch comprising means for searching for an idle trunk line and normally ready and in position to make the said connection through the medium of said terminals whenever the subscriber closes his talking conductors together and thereby sends electric current through the individual switch.

4-8. A telephone system comprising a calling subscribers line conductors normally open at the subscribers station, idle trunk lines, an individual switch provided with a plunger and plunger-controlling magnet, a terminal for each trunk and a corresponding line terminal for each trunk in said switch, and an energizing circuit for said magnet, comprising both of the said line conductors, whereby the said magnet may be energized to positively operate and cause said plunger to connect certain of said terminals to thereby connect the said line with any one of said trunk lines through the medium of said terminals.

49. In a telephone system, subscribers stations including calling mechanism, a plu rality of trunk lines, two switches, one switch for selecting an idle trunk line independently of any operation of said calling mechanism, and thuscxtend a connection over said selected trunk to the second switch, a magnet for maintaining said first switch in contact with said trunk, and means in cluding a circuit extending from said second switch for controlling said magnet.

50. In a telephone system, a plurality of automatic switches, trunks to be seized by said switches, a master switch common to said automatic switches, a pair of normally open contacts, means for initially operating said master switch, means for continuing said operation, means including said contacts for controlling said last-mentioned means, and means 'for controlling said switches over two sides of a line circuit in series.

51. In a telephone system, a plurality of automatic switches, trunks to be seized by said switches, a master switch common to said automatic switches, a motor magnet for operating said master switch, means for initially operating said motor magnet, independent means for continuing said operation after the initial operation, and means for controlling said switches over two sides of a line circuit in series.

52. In a telephone system, a plurality of automatic switches, trunks to be seized by said switches, a master switch common to said automatic switches, a motor magnet for operating said master switch, a relay for initially operating said motor magnet, independent means for continuing said operation after the initial operation, and means for controlling said switches over the two sides of a line circuit in series.

53. In a telephone system, a subscribers line, a plurality of trunk lines extending therefrom, a line switch for connecting with an idle trunk, a magnet for controlling the operation of said switch, means for controlling said magnet over two sides of the line circuit in series, said line circuit being maintained closed until the calling line is connected to the selected trunk.

54. In a telephone system, a subscribers line including a pair of talking conductors, trunk lines, means for selecting idle trunk lines ahead of the calls, automatic means 

